Pneumatic respirator comprising a fluid-operated alternating changeover switch

ABSTRACT

Pneumatic respirator comprising two stages in series. The first stage is a pneumatically operated changeover gas switch an exit of which is connected to a chamber the volume of which may be varied in order to vary the alternation frequency of the switch. The pressure inside the chamber actuates a valve which alternately opens and closes a passage between the respiratory passages of the patient and the source of gas to be insufflated.

United States Patent Monnier 1 Mar. 7, 1972 [54] PNEUMATIC RESPIRATOR 3,522,816 8/1970 Springer l37/8l.5

' COMPRISING A FLUID OPERATED 3,496,956 2/!970 Taplin et al I 37/8 I .5

ALTERNATING CHANGEOVER I FOREIGN PATENTS OR APPLICATIONS SWITCH Inventor: Jean-Pierre Monnier, Clamart, France Assignee: LAir Liquide, Societe Anonyme pour lEtude et IExploitation des Procedos Georges Claude Filed: Mar. 24, 1970 AppliNo; 22,157

Foreign Application Priority Data Mar. 25, 1969 France ..6908694 U.S. Cl. ..128/ 145.8, 137/815 Int. Cl ..A62b 7/02, FlSc 1/12 Field ofSearch ..128/l45.8; l37/8l.5

References Cited UNITED STATES PATENTS I Pavlin et al. 128/1455 658,335 2/1963 Canada l28/l45.8

Primary Examiner-Richard A. Gaudet Assistant Examiner-G. F. Dunne Attorney-Young & Thompson [5 7'] ABSTRACT Pneumatic respirator comprising two stages in series. The first stage is a pneumatically operated changeover gas switch an exit of which is connected to a chamber the volume of which may be varied in order to vary the alternation frequency of the switch. The pressure inside the chamber actuates a valve which alternately opens and closes a passage between the respiratory passages of the patient and the source of gas to be insufflated,

7 Claims, 4 Drawing Figures SHEET 1 OF 4 AWE/WM QT-rm PATENTEDMR 7 I972 SHEET 2 [IF 4 Amwrwe new.

PNEUMATIC RESPIRATOR COMPRISING A FLUID- OPERATED ALTERNATING CI-IANGEOVER SWITCI-I The present invention relates to a pneumatic respirator comprising a fluid-operated alternating changeover switch and, on one of the outlets of the said switch, an. adjustablevolume chamber for varying the alternating frequency of the switch.

It has been proposed to have the alternating changeover switch followed by a switch controlling the ratio between the phase times one of the ways by which the latter switch is controlled is connected to the adjustable-volume chamber by a valve the degree of opening of which controls the ratio between the time periods of throughflow of the fluid in the two outlets of the ratio-controlling switch. The latter in its turn controls, preferably by way of an amplifier switch, a valve which opens and closes the passage of the gas to be insufflated alternately; this valve may be a fluid-operated changeover switch, of small bulk but allowing the gas to be insufflated to escape to the free atmosphere during the exhalation periods of the patient. This valve may also be of the usual pneumatic-actuation type.

This three-stage or four-stage apparatus is fairly complex, which increases the risks of failure. Furthermore, the adjustment of the valve controlling the ratio between the time periods of passage through the two outlets is very tricky; it is scarcely possible to effect this adjustment anywhere except at the factory, which prevents adjusting this ratio during use.

The respirator according to the invention does not have these disadvantages; it is characterized in that the pressure in the said chamber controls a pneumatic-actuation valve which, by means of its closure member, opens or closes a passage between the respiratory passages of the patient and the source of the gas which is to be insufflated. The ratio between times is easily adjusted by means which are easy to set, acting on one or more means controlling the triggering pressure of the pneumatic-actuation valve; examples are described hereinafter. Another advantage of the respirator according to the invention is that it permits controlling the ratio between the time periods of the inhalation and exhalation phases independently of the control of frequency.

The accompanying drawings show, diagrammatically and by way of nonlimitative example, several forms of embodiment of the invention.

FIG. 1 shows a first form ofembodiment.

FIG. 2 shows how the pressure in the variable-volume chamber varies as a function of time.

FIG. 3 shows a modified form of embodiment according to FIG. 1.

FIG. 4 shows in more detail a valve for carrying the invention into effect.

In FIG. I there is illustrated diagrammatically at 2 a fluidoperated alternating changeover switch which is a bistable cell whose control orifices are closed. The gas actuating this changeover switch arrives by way of a duct 4 and passes alternately into an outlet duct 6 the end of which is connected to the free atmosphere, and into another outlet duct 8 debouching into a variable space 10. A cell of this type is described in French Pat. No. 1,568,831.

The duct 8 is also connected by a tube 12 to a chamber 14 of a pneumatically actuated valve 16.

The space is contained in a cylinder 18 and bounded by a piston 20 the position of which can be adjusted by a knob 22. The displacement of the piston modifies the operating frequency of the changeover switch 2 by modifying the volume of the adjustable-volume chamber to which the outlet 8 of the alternating changeover switch is connected; this volume includes not only the space 10 but also the internal volumes of the duct 8, the tube 12 and the volume of the chamber 14.

The valve 16 contains a diaphragm 24 which separates the chamber 14 from another chamber 26 communicating with the atmospheric air by an orifice 28. The diaphragm actuates, by means of a rod 30, a valve head 32 cooperating with a seat 34 to constitute the closure member of the valve. The rod passes through a sealing ring 36.

The gas to be insufflated arrives by way of a union 38, passes through the valve 32, 34 when it isopen, andissues through a union 40 towards the mask worn by the patient. The valve is open when the pressure in the chamber 14, and therefore in the space 10, is sufficient.

The valve head, and consequently the diaphragm, are pushed by aspring 42 in, the direction opposite to the action on the diaphragm of the pressure in the chamber 14.

The spring is pushed by a plate 44 which terminates a screw 46 provided with an operating-knob 48. This screw is in engagement with an internally.screw-threaded hole in the bottom wall 50 of the valve; it permits the spring to be given a more or less considerable compression.

On the force exerted by the spring 42there. depends the ratio between the inhalation and exhalation time periods; this can be explained by means of FIG. 2.

The curve 54 shows how the pressure in the volume 10 varies in accordance with time, owing to the operation of the alternating changeover switch 2. This curve is valid for a certain apparatus and a certain value for the adjustable volume. The abscissae are graduated in seconds and the ordinates in mil- Iibars.

It will be assumed first of all that the spring 42 is adjusted so that the closure member 32, 34 opens under a pressure Po whose ordinate intersects the curve at points 56, 58, 60, 62...The opening time periods are those between the times corresponding to the points 56 and 58, between the points 60 and 62, etc., or about 2 seconds each: during these time periods, the pressure in the space 10 is sufficient to keep the member 32, 34 open. The closing time periods are those between the times corresponding to the points 58 and 60, etc., or about 3 seconds. The ratio between these time periods is, therefore, for the setting of the spring which gives Po as the opening'pressure, equal to 2:3. If, by compressing the spring, this pressure is given the higher value P it will be seen on the graph, by the points 64, 66, 68, 70, that the opening time periods are 1.2 seconds and the closing time periods 3.8 seconds; the ratio has become l.2.:3.8. or 0.32. The sum of an opening and a closing operation remains equal to 5 seconds; this independence relative to the spring 42 makes it possible to calibrate the position of the piston 20 in total time periods of an inhalation and an exhalation.

In reality, operation is slightly displaced by friction, for example friction due to the sealing ring 36; such friction increases the opening pressure and reduces the closing pressure. For example, returning to the setting provided for the pressure Po, the opening is effected at the point 72, and closing at the point 74. Since such friction amounts are practically equal in both directions, the difference in ordinates between the points 56 and 72 is equal and in the opposite sense to that between the points 58 and 74. If furthermore, and as is approximately the case with the curve 54, the two slopes of the curve have the same, constant inclination in the useful field, opening is retarded by as much as closing and therefore the time periods are not modified by friction. A variation in friction during the life of the apparatus, therefore, does not have any influence. This makes it possible to calibrate the position of the screw 46 in time period ratios.

The exhalation of the patient can be effected by an automatic valve arranged on the mouthpiece by which the patient is connected to the respirator.

FIG. 3 shows a variant wherein the opening and closing pressures of the closure member (not shown) of the valve are modified by subjecting to an adjustable pressure the chamber 26 of the pneumatic-actuation valve 76. The spring 42 is adjusted at the factory in order to give, for example, a ratio of time periods equal to unity, which is the maximum which would be desirable in practice.

The pressure in the chamber 26 is supplied by a gas arriving through a tube 78 and expanded to the suitable value by an adjustable expansion valve 80. A manometer 82 measures the pressure which thus completes the action of the spring 42; it is useful to graduate it in ratios of time periods, but then regulation of the spring by the user should not be permitted. A small orifice 84 in the wall of the chamber 26 creates a slight leakage so that the movement of the diaphragm substantially does not change the pressure in the chamber, and so that the pressure in the chamber 26 can be lowered.

It is also possible to create a controllable negative pressure in the chamber 26, but this is generally less convenient since it would be necessary to have a vacuum source available.

FIG; 4 shows a form of embodiment of the valve 76 in more detail.

In the upper portion, the diaphragm 24 separates two chambers 14, 26 formed in plates 86, 88 clamped on the diaphragm by screws 90, 92; the chamber 14 is screwed to the tube 12 by a union 94 and the chamber 26 is connected by a screwthreaded orifice 96 to the outlet of the expansion valve 80, and to a small vent not illustrated here.

A rod 98 is coupled to two plates 100, 102 surrounding the central zone of the diaphragm; it widens into a valve head 104 and a sleeve 106 which guides the spring 42. In the body of the valve there is fitted a valve seat 108 cooperating with the head 104.

The spring bears on the one hand against the end of its guide and on the other hand against an abutment 110 which can be displaced by a screw 112. If it is desired that the variation of the ratio of time periods cannot be effected by the user except by varying the pressure of gas below the diaphragm, access to the screw 112 and to its possible control knob is prevented.

The source of gas to be insufi'lated, for example an expansion valve supplied by a cylinder of compressed air, is connected to the valve 76 by a screw-threaded orifice 114. If the head of the valve is detached from its seat, it allows the passage of gas which, through another screw-threaded orifice 116, issues from the valve and is directed towards the patient by a tube not shown here.

Sealing rings 118, 120 guide the tail 122 of the plate 102 and the sleeve 106 in sealing-tight manner.

The outer diameter of the sleeve is equal to the diameter of the head 104 so that the closure member 104, 108 is balanced when it is closed, as regards the upstream pressure. The diameter of the tail 122 of the plate 102 on which the sealing ring 118 bears is equal to the diameter of the head 104 so that the closure member 104, 108 is balanced when it is closed, as regards the downstream pressure. When the valve is opened, the outer diameter of the tail 122 being equal to the outer diameter of the sleeve 106, the mobile assembly is balanced as regards the pressure which passes through the valve. To balance as regards the pressure in the chamber 26, a duct 124 provides communication between the latter and the space within the sleeve 106 and, by the slight clearance about the abutment 110, with the portion of the sleeve which is situated below the sealing ring 120.

Measurements have been made with a valve of the type illustrated in FIG. 4 and whose spring was adjusted for a ratio between inhalation time period and exhalation time period equal to 1:]; a pressure of 80 millibars in the chamber 26 reduces this ratio to 1:2, which is substantially the desired minimum limit.

The respirator according to the invention can be constructed in ways different from those described. For example, the changeover switch 2 can be of a type disclosed in French Pat. No. 1,530,662. Union 94 may be connected to an auxiliary source of gas with an output limited for example by throttling, said gas escaping from chamber 14 through a valve which is controlled by the pressure inside chamber 10. Pneumatically controlled valves of other types may be used; the spring 42 may be dispensed with if an auxiliary gas pressure is already used for varying the ratio of the time periods.

The respirator according to the invention may be used for any automatic fluid distribution system whose cycle time period and ratio between opening and closing times are to be capable of being easily adjusted; for example, it may be used for the periodic control of a jack.

lclaim: 1. A pneumatic respirator comprising a fluid-operated changeover switch having a plurality of outlets, a source of operating gas connected to the input of said changeover switch, a chamber communicating with one of said outlets, means to adjust the volume of the chamber for regulating the frequency of alternation of the changeover switch, a second source of gas to be insufflated, a mask to be worn by the patient, and a valve having passage means connecting the source of gas to be insufflated and said mask comprising a pneumatic actuation means having a closure member that opens and closes said passage between said mask and the source of gas to be insufflated, said chamber communicating directly and only with said one outlet and with said pneumatic actuation means.

2. A respirator as claimed in claim 1, and a spring in said valve acting on said closure member in the opposite sense to the pressure in the chamber.

3. A respirator as claimed in claim 1, and auxiliary means to exert fluid pressure on said closure member in addition to the pressure of said chamber.

4. A respirator as claimed in claim 2, and means to vary the force of said spring.

5. A respirator as claimed in claim 4, said force-varying means including indicia to indicate the ratios between the inhalation and exhalation time periods for various adjusted positions of said force-varying means.

6. A respirator as claimed in claim 3, and means to vary the fluid pressure exerted by said auxiliary means.

7. A respirator as claimed in claim 2, and auxiliary means to exert fluid pressure on said closure member in addition to the pressure of said chamber. 

1. A pneumatic respirator comprising a fluid-operated changeover switch having a plurality of outlets, a source of operating gas connected to the input of said changeover switch, a chamber communicating with one of said outlets, means to adjust the volume of the chamber for regulating the frequency of alternation of the changeover switch, a second source of gas to be insufflated, a mask to be worn by the patient, and a valve having passage means connecting the source of gas to be insufflated and said mask comprising a pneumatic actuation means having a closure member that opens and closes said passage between said mask and the source of gas to be insufflated, said chamber communicating directly and only with said one outlet and with said pneumatic actuation means.
 2. A respirator as claimed in claim 1, and a spring in said valve acting on said closure member in the opposite sense to the pressure in the chamber.
 3. A respirator as claimed in claim 1, and auxiliary means to exert fluid pressure on said closure member in addition to the pressure of said chamber.
 4. A respirator as claimed in claim 2, and means to vary the force of said spring.
 5. A respirator as claimed in claim 4, said force-varying means including indicia to indicate the ratios between the inhalation and exhalation time periods for various adjusted positions of said force-varying means.
 6. A respirator as claimed in claim 3, and means to vary the fluid pressure exerted by said auxiliary means.
 7. A respirator as claimed in claim 2, and auxiliary means to exert fluid pressure on said closure member in addition to the pressure of said chamber. 